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Bogging above 3500 rpm

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My 01vlx has been performing well last season and this season since i had cleaned injectors, replaced hoses, added secondary fuel pump, installed new primary pump, and usual tune up parts. I started with fresh filters this year and all has been good. Ive had a few dings on the prop this year though and i may notice just a hint of vibration although its not noticeable unless you are looking for it. I do have a prop ear with a noticable dent to it. Last weekend i noticed after running mostly 3000 rpm i was heading toward the dock and decided to go WOT for a few seconds. The engine just bogged like crazy or at least you felt and heard the lower pitch roar and it seemed like there was a good deal of drag that caused the boat to slow a bit. Once i pulled back some, the engine sounded right. I could add just a hair of throttle and i could feel the boat speed up. Its like if i went more throttle very slowly, the speed would creep up as did the rpm. If i gave it a goose of throttle then the engine would bog and i would feel a deceleration. Could the prop do that? Hope the fuel pumps arnt going south again. 

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It doesn’t sound like a prop issue to me. Have you tested your throttle position sensor?

Remove the TPS connector, stick some small gauge wire into the signal (blue) and ground pins (black), and re-install the connector. Turn the key to ignition (don’t need to start it) and measure the voltage drop with a voltmeter over the full range of throttle position. Should start close to 0V and increase to 5V without any sudden jumps. If it doesn’t, you’ve got a bad TPS.

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  • 2 weeks later...

Well i checked tps and it checked good. Went smoothly up to 4.5 volts at wot during testing. I was out again last week and it seemed to act the same. Good running up until about 3500 and then seems to fall off. I dont do anything above 3500 except run fast. It was fine about a month ago. 

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  • 4 months later...


Took off fuel pump and filter i had added. Found one of my custom made hi pressure hoses between fuel pump and hi pressure filter was boubleing up inside restricting the flow. Still not sure the pump is perfect though so how do i get a pump bench tested? Can i do it at home? What kind of fluid do i use to pump with it while bench testing?

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17 years of fuel running thru 18 year old fuel line coupled with the additives in fuel over the past decade will cause clogging in the system.

Chasing a fuel delivery problem is just that...a chase.  I’d suggest new fuel hoses new filters and pulling injectors and having the professionally serviced.  If you still have a problem, then we can look st fuel pump.  My money is in clogged injectors that can’t deliver needed fuel volume st higher RPM.

Edited by Murphy8166
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First post in this thread says it all. I already fully rebuilt and customized and cleaned injectors. This issue is after having a couple good seasons. End of this season engine started not having power once i hit about 3500 rpm. I hqve found an internal buldge of the 2 season custom fuel line. I may hqve caused the damage since i flexed the high pressure hose to bend it to the side to drain the 8 micron after pump filter. Id like to verify the pump before i put it all back together for this spring.

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Had the same problem with my 03 and did most of the same troubleshooting steps. For me it ended up being the ICM (ignition control module) mounted in the distributor. It was like a new boat after changing that part.

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